Installing a Python module in Blender's Python API
Python loads any module from the directories in sys.path. Try this in the interactive Python console in Blender:

import sys
print('\n'.join(sorted(sys.path)))


That'll give you a choice of paths. Alternatively, you can place your scripts next to your blend file, and in the blend file text editor itself have a script like this:

import bpy
import sys

p = bpy.path.abspath('//scripts')
if p not in sys.path:
    sys.path.append(p)


Make sure the script name ends in .py and the 'Register' checkbox is checked. After this runs you can import Python modules from the scripts subdirectory of whichever directory holds your blend file.

Also make sure that the directory names are actually valid Python names, so without spaces.